1. Field of the Invention
The present invention is broadly concerned with improved drying apparatus of the agitated bed type which can be used for heating and drying of an almost limitedless number of particulate products. More particularly, the invention pertains to such apparatus, and corresponding methods, wherein an essentially imperforate, flexible bed is provided together with a series of agitators located below and spaced along the length of the bed and oriented for repeatedly impacting the bed in order to generate an undulating bed movement serving to elevate and tumble the particulate material; a number of infrared heating units are disposed above the bed for directing IR energy onto the particulate material as it is being elevated and tumbled. This creates a most efficient drying environment.
2. Description of the Prior Art
A vast number of drying devices have been proposed in the past for processing particulate materials. Among these are the well known drum dryers which have long been used for drying alfalfa and other agricultural products. A constant goal in the development of dryers is the most efficient drying of particulates, i.e., in the shortest time and with the smallest energy inputs.
U.S. Pat. No. 5,557,858 describes an infrared drying apparatus made up of an infrared radiant energy source adjacent a series of stacked, looped conveyor belts for handling particulate material. The use of flameless catalytic gas fired infrared heaters in this context has proven to be a decided advance in the art.
Canadian Patent No. 993,259 describes an apparatus for treating seeds through the use of IR radiation wherein the seeds are supported on a perforate steel wedge-wire conveyor allowing passage of air through the conveyor. As noted in the '259 patent, the nature of the metal conveyor used in conjunction with the wavelength of the IR radiation are vital factors in obtaining good results.
U.S. Pat. No. 5,037,537 describes a size classification device used for separating fines from wood chips. In this device, a perforate or foraminous bed is employed together with a series of rotatable beater bar units underlying the bed. Fines are allowed to pass through the bed and are collected below, thus effecting separation of the fines from the larger wood particles. Use of perforated beds as described in the '537 U.S. and '259 Canadian patents has been found to be troublesome. In particular, particulates tend to clog the openings thus defeating the very purpose of providing a perforated bed. Moreover, the beds described in the '537 patent are believed to have short useful lives because the beater bar units tend to tear and destroy the bed.